System and Method of Detecting and Locating Intermittent Electrical Faults in Electrical Systems

ABSTRACT

Signals are transmitted from at least one transmitter that is positioned in an electrical network. The signals that have been transmitted are received by the at least one single receiver at a single receiver positioned within the electrical network. At the single receiver, the received signals are analyzed and a determination from the analyzing the received signals is made as to whether a fault has occurred in the electrical network.

CROSS REFERENCES TO RELATED APPLICATIONS

Application entitled “Housing Arrangement for a Fault DeterminationApparatus and Method of Installing the Same” naming Charles Kim asinventor and having Attorney Docket No. 93598 and being filed on thesame day as the present application, and provisional application No.60/846,718 entitled “Method of Detecting Intermittent Faults inElectrical Wire by Utilizing Data Communication Error Over Time,” namingCharles Kim as inventor, filed Sep. 24, 2005, the contents of both ofwhich are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This application relates to approaches for detecting and/or locatingelectrical faults in electrical systems or networks.

BACKGROUND

Intermittent electrical faults are physical events that manifestthemselves occasionally and in often unpredictable ways withinelectrical systems or networks. When an intermittent fault occurs in asystem, the system may produce erroneous results or could fail. To takesome specific examples of particular electrical faults that occur innetworks, a wire may rub against a neighboring wire and a smallelectrical arc may be created as a result of the contact. In anotherexample, a clamp may break through the insulation surrounding the wireand touch the wire creating a fault. In yet another example, a wire maybreak at the back end of a connector thereby creating a fault. In stillanother example, corrosion may create intermittent non-contact betweenwires and pins within a given system. In another example, cracks onwires within the system may have water dripping on them (or the wiresmay be in contact with other substances) thereby creating electricalfaults. Internal coil turn-to-turn insulation in electric machines mayalso fail in systems with electrical coils creating electrical faults.

The consequences of intermittent electrical faults can be severe and, inmany instances, can cause substantial damage to the electricalequipment, can result in injury to users, or can even cause the loss ofhuman life. For instance electrical fires may be sparked because of theoccurrence of some electrical faults. When the faults occur in aircraft,fuel tank explosions may occur if electrical faults occur near a fueltank. Even if catastrophic damage or injury does not occur, theoperational lifetime of machines or systems may be reduced as the resultof the occurrence of intermittent electrical faults. One characteristicof intermittent faults is that they are random and unpredictable. Theirrecurrence is also unpredictable. However, if an intermittent fault isleft undetected and un-repaired, a major, disastrous, and permanentfault might follow that may cause deaths, failures, or destruction.

Previous attempts at identifying electrical faults have relied upon thevisual or instrument-aided inspection of electrical systems. However,various disadvantages exist with these previous approaches. For example,the operation of the system frequently had to be suspended to determineif a fault existed thereby causing various problems such as loss ofrevenue for the owner or operator of the system. Moreover, manylocations within existing systems were frequently hard to reach and/orobserve thereby severely limiting the effectiveness of these approaches.These previous approaches also proved unable to detect the fault in manycases since the duration of the fault was often short and the systemwould behave normally as if nothing happened after this short-livedintermittent fault event. Therefore, it was relatively easy for theobserver to miss the occurrence of the fault. Additionally, theseapproaches often relied upon intrusive placement of any equipment usedfrequently leading to at least some disruption of the existing system.

Other previous approaches relied upon transmitting electromagnetic wavesacross the network being observed. In one previous example, pulses weretransmitted in networks and any reflections were analyzed to determineif a fault existed. More specifically, incident standing waves orimpulses were transmitted and then reflected in the network, and thenthe time between the incident pulse and the reflected pulse wascalculated to determine the distance to the location where the pulse wasreflected. Different criteria were then used to determine if thereflection was a potential fault. One problem with this technique wasthat any change in the wire material (e.g., a branch-out in the network)reflected the incident waves resulting in erroneous fault determination.Another problem with this technique was that it required thetransmission of high voltage pulses, which some electrical systems withthin coils (e.g., with short wires or thin windings) could not endure.Another time domain reflectometry method employed spread-spectrumtechniques, but this approach did not solve the above-mentioned problemssince high voltage pulse transmission was still required and reflectionstill occurred on branches of the electrical network.

Another previous approach transmitted direct-sequence spread-spectrummodulated signals, instead of high voltage signals, and employed signalprocessing techniques in an attempt to find and locate electricalfaults. These approaches, however, still relied on reflectometry thatis, sending incident signal and receiving reflected signal and thetiming of them for distance calculation. As a result, although thisapproach may have, under some circumstances, overcome the need to usehigh voltage incident voltage pulses, it still had the problem ofreflection occurring at all points of branching in the network and inthe devices that were connected.

Still another problem of the reflectometry approach was that thelocation of the device must be close to one end of the electricalsystem, either the line end or the source end. Otherwise, the injectedsignal would be reflected from both ends and result in a combined,distorted, and reflected signal. This requirement of locating the deviceat either end is very difficult to meet since many electrical networksare connected in a complicated format, often in a mesh architecture.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 comprises a block diagram of a fault determination systemaccording to various embodiments of the present invention;

FIG. 2 comprises one example of a byte-map for use in a faultdetermination system according to various embodiments of the presentinvention;

FIG. 3 comprises a block diagram and fault determination tableillustrating one approach for fault determination according to variousembodiments of the present invention;

FIG. 4 comprises a block diagram of a fault determination apparatusaccording to various embodiments of the present invention;

FIG. 5 comprises a flow chart of one approach for determining faultsaccording to various embodiments of the present invention;

FIG. 6 comprises a flow chart of one approach for determining faultsaccording to various embodiments of the present invention;

FIG. 7 comprises a block diagram and flow chart of one approach fordetermining electrical faults according to various embodiments of thepresent invention;

FIG. 8 comprises a block diagram of a transmitter and receiver accordingto various embodiments of the present invention; and

FIG. 9 comprises a block diagram of a transmitter or a receiveraccording to various embodiments of the present invention.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions and/or relative positioningof some of the elements in the figures may be exaggerated relative toother elements to help to improve understanding of various embodimentsof the present invention. Also, common but well-understood elements thatare useful or necessary in a commercially feasible embodiment are oftennot depicted in order to facilitate a less obstructed view of thesevarious embodiments of the present invention. It will further beappreciated that certain actions and/or steps may be described ordepicted in a particular order of occurrence while those skilled in theart will understand that such specificity with respect to sequence isnot actually required. It will also be understood that the terms andexpressions used herein have the ordinary meaning as is accorded to suchterms and expressions with respect to their corresponding respectiveareas of inquiry and study except where specific meanings have otherwisebeen set forth herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Approaches are provided to detect the presence and locations of faultswithin an electrical network. The approaches utilize one or moretransmitters to send signals (e.g., packets) to one receiver and, basedupon the mismatch between the signal sent and the signal received at thereceiver due to the distortion in the signal transmission caused by thetransient of intermittent fault, to determine the presence and/orlocation of electrical faults. The approaches described herein are easyand cost effective to use, do not rely upon the transmission of highvoltage signals, can be installed at any location within the electricalnetwork, are an effective detection solution for the unpredictableintermittent event of faults that occur between transmitter andreceiver, and are not susceptible to the false fault indicationsobtained in previous approaches.

In many of these embodiments, signals are transmitted from a pluralityof transmitters that are positioned in an electrical network. Thesignals transmitted by the transmitters are received at a singlereceiver positioned within the electrical network. At the singlereceiver, the received signals are analyzed and it is determined fromthe analysis of the received signals whether a fault has occurred in theelectrical network between transmitters and receiver. The location ofthe fault may also be determined.

In some examples, a random pause duration is inserted betweensuccessively transmitted signals. Each of the plurality of transmittershas an associated unique combination of bits that uniquely identifiesthe transmitter and the unique combination bits is included in thesignals sent to the receiver. The receiver analyzes the receivedcombination of bits and compares the combination of bits to an expectedcombination of bits (expected to be received from the transmitter) andwhen there is not a match, determines that an electrical fault exists inthe segment of the electrical network between the transmitter and thereceiver. The location of the electrical fault may also be determinedbased upon the analysis.

In other examples, each of the plurality of transmitters receives acommand signal from the single receiver. Each transmitter only transmitssignals to the single receiver when the command signal has been receivedat the selected transmitter. The total absence of an expected messagefrom a transmitter or the mismatching of any message received (comparedto an expected value) of a message sent in response to the commandsignal indicates the existence of open circuit or potential faults.

Referring now to FIG. 1, one example of an approach for determining anddetecting electrical faults in an electrical network 100 is described.An electrical interconnect backbone 102 is coupled to transmitters 104,106, 108, 110, 112, 114 and 116 via electrical branches 120, 122, 124,126, 128 and 130 respectively. The electrical interconnect backbone 102is also connected to a receiver 118. The electrical interconnectbackbone 102 may be any type of electrical connection of any voltagelevel or any current type, e.g., direct or alternating. For instance,the backbone 102 may include two wires (e.g., one ground and the other awire transmitting a DC current and voltage). Other examples of backbonearrangements and any number of electrical wires are possible todistribute electrical power. In one example, electrical sources havingvoltages of approximately 100 vRMS (or 28V DC) are distributed acrossthe backbone 102 and the branches of the network 100.

The transmitters 104, 106, 108, 110, 112, 114 and 116 are any type ofdevice capable of transmitting any type of modulated communicationsignal, over electrical circuit 102 without compromising the powerdelivering function of the electrical network 102, that includes anytype of information. For example, the transmitters 104, 106, 108, 110,112, 114 and 116 may include controllers to form packets or messages,modems to convert the messages to suitable signals through modulation(e.g., having the proper voltage levels) for transmission, and acoupling network to provide filtering and protective functions toconnect any of the transmitters to the electrical interconnect backbone102. As mentioned, the transmitters 104, 106, 108, 110, 112, 114 and 116may operate and transmit packets or messages at any voltage levelappropriate for the electrical interconnect backbone 102.

The receiver 118 is any device capable of receiving modulatedcommunication signals from any of the transmitters 104, 106, 108, 110,112, 114 and 116 via the electrical interconnect backbone 102. As withthe transmitters 104, 106, 108, 110, 112, 114 and 116, the receiver 118may include a controller, a modem and a coupling network. As mentioned,the coupling network buffers the receiver or transmitter from theelectrical interconnect backbone 102 by a filtering function so that thereceiver or transmitter insulates it from the high voltages of theelectrical network while effectively sending and receiving the modulatedsignal. The modem in the transmitter modulates the digital signal formedby the controller and the modulated signal travels through the couplingnetwork into the electrical network. The modem in the receiver acceptsthe modulated signal via the coupling network sent from thetransmitters, demodulates the signals into a digital byte format, andsends the digital data to its controller. The receiver controllerprocesses the signals for data errors or mismatch to determine whether afault has been detected or the likelihood that a fault has been detectedand/or the possible location of faults. Various error rates can bedetermined from the process.

The receiver 118 communicates with a port 132 and the port 132 iscoupled to an external device 134. The external device 134 may be apersonal computer, display, enunciator or any other type of device thatis capable of alerting a user that a fault has been detected somewherein the network 100. The location of faults and message error ratecalculated for the location may also be displayed to give the severity(likelihood) or status of the fault progress. In an alternativeapproach, the external device 134 may provide some or all of the faultdetermination processing capabilities rather than the receiver 118 whenthe receiver 118 is limited to provide the mismatch or error occurrenceonly.

In one example of the operation of the system of FIG. 1, thetransmitters 104, 106, 108, 110, 112, 114 and 116 transmit messages tothe receiver 118. The receiver 118 analyzes the messages that itreceives and based upon the results of the analysis determines whether afault exists, the likelihood that a fault exists, and/or the possible(or determined) location(s) of faults (e.g., within a particular branch120, 122, 124, 126 and 128 or 130 of the network 100). It will beappreciated that although a single receiver is shown in the example ofFIG. 1, any number of receivers may be used in the network 100.Additionally, any number of transmitters may be employed in the network100.

Once errors are detected and/or their locations determined remedialaction can be taken. For example, a user can access the potential siteof the error, determine if a problem exists, and, if a problem existsremedy the problem (e.g., replace a wire).

Referring now to FIG. 2, one example of a message format for messagestransmitted according to the approaches described herein is described. Amessage or packet 200 includes a preamble byte 202, a receiverinformation byte 204, a transmitter information byte 206, and 4 to mmessage bytes 208 where m is an integer greater than 4. In one approach,each transmitter within the system (e.g., transmitters 106, 108, 110,112, 114, or 116 of FIG. 1) has a uniquely identifiable message byte(e.g., some unique pattern of binary ones and zeros) that is known tothe receiver and that uniquely identifies a transmitter (e.g., thereceiver 118 of FIG. 1). All information in the message or packet 200 isincluded in the data stream that is transmitted to the receiver.

To detect an error or fault, in one approach, the receiver compares thedata received from the transmitter against pre-assigned data that it hasstored regarding each transmitter. In the case of a mismatch between thereceived data and the expected data, a fault is potentially detected.The non-reception at the receiver of an expected message or packetexpected to be sent from the transmitter may also indicate the existenceof a fault in the form of open circuit in the network.

For transmissions across the network, various approaches may be used toensure signal integrity (e.g., to ensure signals sent by multipletransmitters do not interfere with each other). In any approach used,the modem of each transmitter monitors the wire via a “carrier detect”approach that detects if there are any modulated signals on the wire,and waits to send its signal until there is no signal on the wire.Therefore, at any one moment, only one transmitter is allowed to sendsignals. In one approach, multiple transmitters send signals without thecontrol of the receiver. To ensure signal integrity, a random pauseduration is inserted after each signal transmission. Each transmitterhas an equal chance to send a signal to the receiver and, therefore,each wire segment (e.g., each branch of the network) is monitored at thesame priority with an equal chance of detecting errors compared with anyother electrical branch.

In another approach that may be used to achieve signal arbitration, onlya transmitter that is ordered by the receiver is allowed to send asignal. In other words, the receiver is the master of this single-masterand multiple-slave protocol. The receiver sends a message or packet(e.g., a command) to a transmitter, for example, the message of FIG. 2.After the transmitter receives the message or packet from the receiver,this message is copied and sent back to the receiver. The comparison ofthe received message at the receiver against the sent message determinesif there is an error in the signal, which in turn indicates that a faultexists in the wire segment between the receiver and the commandedtransmitter. In some approaches and as described elsewhere herein, anerror is detected if no return message is detected by the receiver(e.g., within a predetermined amount of time), indicating possibledisconnected, open circuit.

Referring now to FIG. 3, one example of using these approaches to detectan error or fault in a network 300 is described. In this example, anelectrical backbone 302 is coupled to transmitters 304, 306 and 308 anda receiver 310. The network 300 is divided into segments S1, S2 and S3and branches Br1, Br2 and Br3.

A table 312 is stored in a memory at the receiver and used to determinethe possible location or locations of electrical faults within thenetwork 300. For example, using the techniques described herein, it isdetermined if a particular error exists in one of the branchesassociated with a particular transmitter. For example, the mismatch ofexpected data from the transmitter 304 versus expected data, while thereis no mismatch from the transmitters 306 and 308, may indicate that afault exists in branch Br1.

To take a few examples and utilizing the table 312, if no errors aredetermined for transmitters 304, 306 and 308, no fault exists in thenetwork. In another example, if no errors are detected at transmitters304 and 308, but an error is detected at transmitter 306 then a faultmay exist at segment S2 and/or both branches Br2 and Br3. It will beappreciated that the table 312 maybe any type of data structure and isalso not limited to the format shown in FIG. 3. Moreover, the examplesshown in table 312 may vary depending upon the placement of thetransmitters and the receiver and the exact configuration of the networkor other circumstances.

Referring now to FIG. 4, one example of a transmitter or receiver 400 isdescribed. The device 400 can be configured to operate as either atransmitter or receiver and includes a controller 402, a modem 404, acoupling network 406, and a memory 408.

If used as a transmitter, the controller 402 may form messages (e.g.,packets) to send to a receiver via the modem 404 and coupling network406. The modem 404 forms signals according to appropriate voltage levelsor protocols and the coupling network 406 provides appropriate bufferingand/or filtering capabilities that protect the modem 404 and controller402 from electrical hazards (e.g., overvoltage conditions) present onthe backbone and, at the same time, effectively inject the modulatedsignals into the backbone.

If used as a receiver, the coupling network 406 filters in only themodulated signal from the backbone and the modem 404 demodulates thesignal into digital data and sends it to the controller 402. As areceiver, the device 400 may store in the memory 408 a table as has beendescribed above with respect to FIG. 3. The controller 402 then mayperform an analysis to determine the potential location or locations offaults within a particular network. Further, the controller 402 may becoupled to a port, which communicates with external devices to indicateto a user the presence and potential locations of faults. Further, thecontroller 402, modem 404, and/or coupling network 406 may be coupled toan external power supply.

Referring now to FIG. 5, one example of a transmission arbitrationprotocol is described. At step 502, a message or packet is sent from atransmitter. For example, the message maybe in the format as indicatedin FIG. 2. At step 504, after the message is sent, a random pauseduration is inserted after the message. Then, the same message is sentagain, and this process continues, and to take one example, the receivercompares the received message to the expected message and determinesthat a fault exists if there is a mismatch. When a mismatch exists, apotential fault may exist in the portion of the network associated withthe transmitter that sent the message.

Referring now to FIG. 6, another example of a transmission arbitrationprotocol is described. At step 602, a transmitter waits to receive amessage from a receiver. At step 604, after receiving a message thetransmitter echoes the same message back to the receiver. Then, it waitsfor another command from the receiver. In the meantime, if the receivernever receives an echoed message back (e.g., after waiting for apredetermined time period) or the message returned to the receiver is inerror (as would be indicated by a comparison of the received messagewith the expected message), then a fault (including open circuit) isindicated to exist.

Referring now to FIG. 7, another example of approaches for faultdetermination is described. As shown in FIG. 7, through a couplingnetwork and modem 761, a packet 701 (having pre-set values) is sent fromtransmitters 702, 704, and 705 to a controller 703 of a receiver, andread through serial communication port 736 of the controller 703.

The packet 701 includes, for example, preamble byte 732, and atransmitter identification byte 733, and a packet number byte 734,followed by n data bytes 735, D1 through Dn. N may be any integer value.In one example, n=24 and, consequently, 24 bytes of data are used. Therate of the data transmission, or bit rate, can become any speed or anymodulation scheme suitable for the modem. In the some examples, a 2400bps power line modem is used that provides approximately 130 kHz ofFrequency Shift Keying (FSK) modulation. However, other numbers of databytes may be used along with other bit rates and other modulationschemes. In some examples, a longer packet with slower bit rate with amodulation scheme may have better chance of intermittent fault detectionthan a shorter packet with higher bit rate with another modulationscheme.

The controller 703 of the receiver, after detecting the preamble byte732, followed by identification byte 733, then reads the rest of thebytes (step 760) one at a time and store the packet into internal memoryspace 741. In another part of the memory 741, the packet 701 is storedas a packet 742 and is used for a comparison with an expected (andpreviously stored) packet 743. The expected packet 743 includes theexpected values of information for the packet 742. The packetinformation stored in memory can be compared against each of thetransmitters.

The controller 703 at step 762 reads the stored packets 742 and 743 andmakes a bit-by-bit comparison of all n data bytes against the pre-setvalues of the n data bytes between the packets 742 and 743. The firstanalysis is to decide which transmitter sent the packet and thesubsequent analysis result for packet mismatch is stored and associatedwith the transmitter. If the two packets are the same, then the resultof no error is registered for the transmitter. Then, with for example,the decision table of FIG. 3, a fault detection and location decision ismade and displayed 753 or uploaded to an upper level computer 755. Then,the next packet sent from a transmitter is read at step 762.

At step 764, the error details (including the identity of thetransmitter that sent the packet) may be stored. At step 766 it isdetermined if an adequate number of packets has been received in orderto determine whether an alarm should be given a user. If the answer atstep 766 is negative, control returns to step 760. If the answer isaffirmative, execution continues at step 768 where a comparison is madewith a threshold 770. If the number of erred packets exceeds thethreshold, a result 772 is formed as a fault (e.g., “1”) or no-fault(e.g., “0”) result of a particular transmitter as in the table of FIG.3. The final decision on fault determination using the table (stored inmemory) is made and communicated to one or more of a port 750 (fordisplay on an enunciator 751), a communication port 752 (forpresentation on a display 753) and/or port 754 (for display on apersonal computer 755). Depending upon the type of display, graphicalimages maybe formed to be displayed on some or all of the mentionedexternal devices.

As described herein, a pause may be inserted between transmittedpackets. In one example, the pause between two consecutive packets, in asystem using a microcontroller of 8-bits and 20 MHz speed, is about 100milliseconds. The pause time is selected so as to be sufficient forprocessing to occur. For example, the pause duration may be selected toallow for the fault determination process to finish and also for errormessages to be sent to external devices (e.g., the enunciator 751, thedisplay 753, and/or the personal computer 755). The pause duration canalso include time to allow processing to occur for a given number ofpackets, for example, 1000 packets.

The threshold level of the rate of error that initiates the fault (e.g.,“1”) or no-fault (e.g., “0”) can be any predetermined value or,alternatively, be determined after a run of the system under cleanelectrical wire status. Further, the threshold can be automaticallydetermined using the error rate by comparing the error rates duringactual/normal operating status and those of actual intermittent faultstatus. Before deploying the above-mentioned approaches, a test run maybe executed in a staged intermittent fault condition that sets thethreshold level for a fault or no-fault boundary, and thus increases thedetection probability while at the same time decreasing false alarm andnuisance readings.

Various error rates can be determined. For example, a first error typethat can be calculated is a Net Packet Error Rate (NPER), which is thepercentage of packets that contained errors out of the total number ofreceived packets. In the NPER case, the lost packets by the error inidentification byte(s) are ignored.

Alternatively, a Total Packet Error Rate (TPER), can be calculated. Thisrate is the percentage of the number of packets received with error outof the total number packets sent.

In another example, a Net Byte Error Rate (NBER) can be calculated. TheNBER is the percentage of the number of packets received with just 1data byte error caused by 1 or 2 bit errors in the byte out of thereceived packets with no error. The NBER focuses, unlike NPER or TPER,on very short disruptions. Very short disruptions in time rooted from anintermittent fault may cause error in a bit or two in a byte data, notacross the data bytes.

Yet another alternative error rate that can be determined is the TotalByte Error Rate (TBER), which is the percentage of the number of packetsreceived with 1 data byte error caused by 1 or 2 bit errors in the byteout of the total number of packets sent. The TBER ignores anydisruptions which are long enough to cause errors in multiple databytes. This rate does not include or consider long disruptions possiblycaused by normal switching operations and, as such, could reduce thenumber of false alarms.

Referring now to FIG. 8, a receiver 801 receives packets over electricalwires 810 and 811 that are transmitted by a transmitter 802. If theelectrical wire carries DC current, then one of the wires 810 or 811 canbe a ground wire. In the example of FIG. 8, both the receiver 801 andthe transmitter 802 have the same functional structure and includes apower line modem 802 or 804 and a controller 803 or 805. The receiver801 includes additional interface outputs or ports 812, 813 and 814. Theoutput 813 is connected to an indicator/enunciator 807 to send an alarmwhen an intermittent fault is detected. This may be in the form ofblinking light (e.g., light emitting diode (LED))and/or audibleindication. The port 813 is used to display the alarm condition on adisplay 806 (e.g., a liquid crystal display (LCD)) with texts andgraphics. The output 814 is further used to send the alarm condition toa computer system 820 via serial communication port 808 for displayingon a computer screen or for further analysis of the alarm conditiondata. The errors and error rates discussed herein can be displayedaccording to any of the display approaches described herein.

The transmitter 802 includes the power line modem 804 and the controller805. The controller 805 is a microcontroller or microprocessor whichincludes computing code, controls digital logic, and sends bytes ofdigital data (e.g., packets). The computing code manages the number ofpackets sent and how often the packets are sent.

Referring now to FIG. 9, one example of a transmitter 900 is described.A power line modem 921 in the transmitter 900 receives the seriallytransmitted digital data stream from a controller 903, converts thedigital data to analog data, and modulates the analog data in FSK(Frequency Shift Keying) scheme (in which digital logic 1 is coded toanalog signal of a certain frequency and digital logic 0 is to anotherfrequency). The modulated signal is amplified by an amplifier 922 andsent through a coupler 923, which sends the modulated signals and blocksall other signals outside the frequency band, to the electrical wires910 and 911.

The modern 921 may be any commercially available modem chip. The modem921 may include a filter that band passes only the frequency band usedin the particular FSK scheme that is employed. The modem 921 has fourcontrol and data communication lines with the controller 903. Theseinclude RX control 930 for controlling the reception of digital data, TXcontrol 931 for controlling the transmission of digital data, carrierdetect (CD) control 932 for indicating to the controller 903 if and whenthe modem 922 receives a modulated signal from an electrical wire, andRX/TX control 933 for indicating if a digital signal has been receivedand is to be transmitted.

A modulated signal automatically is transmitted from the modem 921 andamplified by the amplifier circuit 922. The amplified modulated signalthen is presented to the electrical wires via a coupler 923, whichpasses the signals of the frequency band and blocks all other signals.The coupler 923, in one example, is a transformer coil 924 withfiltering capacitors 925 and 926. In one approach, the structure of thereceiver is identical (or nearly identical with the receiver havingports to communicate with external devices) with the structure of thetransmitter 900.

Various transmission protocols may be used. For example, a byte of anydata can be sent from the receiver to indicate to the transmitter tosend data.

A packet may be sent to the receiver with various bytes of data. Forexample, a preamble byte may be included. The next byte is sent toidentify the transmitter and the receiver. To take one example, if theidentification byte is a preset data value such as a byte data of10110011, then the receiver checks if the received identification byteis 10110011. If the received identification byte is the same as thepreset data, then the receiver is now ready to receive the data streamthat follows. One or more bytes can be used for identification purposes.

As mentioned, in one example, the group of data bytes including thepreamble, identification, and actual data form a packet. In oneapproach, one packet is transmitted from a transmitter and reception ofthe same one packet made by a receiver. In one approach, the transmittertransmits the same one packet repeatedly, with a pause between twopackets, until, for example, a set number of packets are sent (e.g., 956packets). Then, packet transmission resumes. Under an intermittent faultcondition, the preamble byte may be noised out, or the identificationbyte may be contaminated, then the receiver ignores the packet with thecontaminated identification byte since the packet is interpreted as notmeant to be sent to the receiver. In this case, one packet is lost and apacket error exists.

Thus, approaches are provided to detect the presence and locations offaults within an existing electrical network. The approaches utilize oneor more transmitters to send signals (e.g., packets) to one morereceivers and based upon the signal received at the receiver, todetermine the presence and location of electrical faults. The approachesdescribed herein are easy and cost effective to use, do not rely uponthe transmission of high voltage signals, can be implemented at anyplace within the electrical system, and are not susceptible to falseresults as have been obtained in previous approaches.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention.

1. A method of determining intermittent electrical faults comprising:transmitting signals from a plurality of transmitters that arepositioned in an electrical network; receiving the signals transmittedby each of the plurality of transmitters at a single receiver positionedwithin the electrical network; and at the single receiver, analyzing thereceived signals and determining from the analyzing of the receivedsignals whether a fault has occurred in the electrical network.
 2. Themethod of claim 1 wherein transmitting the signals comprises inserting arandom pause duration between successively transmitted signals.
 3. Themethod of claim 2 wherein each of the plurality of transmitters has anassociated unique combination of bits that uniquely identifies thetransmitter and wherein the unique combination bits is included in thesignals sent to the receiver.
 4. The method of claim 3 wherein thereceiver analyzes the received combination of bits and compares thecombination of bits to an expected combination of bits and when there isnot a match, determines that an electrical fault exist.
 5. The method ofclaim 4 further comprising determining the location of the electricalfault based upon the analyzing.
 6. The method of claim 1 whereintransmitting the signals comprises receiving a command signal from thesingle receiver at a selected transmitter and only transmitting thesignal from each of the selected transmitter to the single receiver whenthe command signal has been received at the selected transmitter.
 7. Afault determination system comprising: a plurality of transmitters, eachof the plurality of transmitters configured to transmit signals acrossat least a portion of an electrical network; and a single receivercommunicatively coupled to the plurality of transmitters, the singlereceiver configured to receive the signals transmitted by each of theplurality of transmitters and to analyze the received signals anddetermine from analyzing the received signals when a fault has occurredin the electrical network.
 8. The system of claim 7 wherein the each ofthe plurality of transmitters is configured to insert a random pauseduration between successively transmitted signals.
 9. The system ofclaim 8 wherein each of the plurality of transmitters has a uniquecombination of bits that identifies each transmitter and the uniquecombination of bits is included in signals sent to the single receiver.10. The system of claim 9 wherein the single receiver is configured toanalyze the received bits and to perform a comparison between thereceived bits to expected bits and when a match does not exist betweenthe received bits and the expected bits, to determine that a faultexist.
 11. The system of claim 10 wherein the single receiver isconfigured to determine the location of the fault based upon thecomparison between the received bits and the expected bits.
 12. Thesystem of claim 7 wherein each of the plurality of transmitters isconfigured to receive a command signal from the single receiver and toonly transmit a signal to the single receiver after the command signalshas been received.
 13. The system of claim 7 further comprising anexternal device that is coupled to the single receiver.
 14. The systemof claim 13 wherein the external device is selected from a groupconsisting of an enunciator, a display, and a computing device.